1. THE ABILITY TO CAUSE CHANGE 1

2. mechanical energy 2 T y p e s o f E n e r g y Radiant energy

3. types of energy oToThermal energy - from the motion of molecules oCoChemical Energy – mostly among chemical bonds oNoNuclear energy - from the nuclei of an atoms oEoElectrical and Magnetic energies – E&M interactions oRoRadiant energy -- carried by electromagnetic waves oMoMechanical energy – usually by large bodies 3

4. Energy Energy is the capacity (ability) to do work. Kinetic Energy: Associated with an object in motion Potential Energy: Is the interaction energy of an object wit another 4 CLIP

5. Foundations of Engineering Chapter 22

6. Accounting for Energy - Part 1 Chapter 22

7. RAT 1 Turn off your monitors, close your books and notes.

8. RAT 1 As an INDIVIDUAL, you have 3 minutes to answer the following questions: A) Name three types of work B) Name two types of potential energy C) Name two types of kinetic energy

9. Objectives Understand what energy is Understand path energies Work (specific classification; see next) mechanical, shaft, hydraulic, electrical, photon… Heat conduction blackbody radiation

10. What is energy? Let’s define in the most general way Work first Work is a change in the universe Energy – is the source or driving force able to perform such a work Thus, work done on x changes the x energy

11. Energy Make an analogy for energy: money is a “unit of exchange”, Example 1 car = $20 k 1 house = $100 k 5 cars = 1 house =

12. Energy Equivalents 1 kg coal = 42,000,000 joules 1 kg uranium = 82,000,000,000,000 joules (82x10 12 ) 1 kg uranium = 2,000,000 kg coal!!

13. Energy is a conserved quantity Generally, energy is a conserved quantity, i.e., generation and consumption are zero. In fusion and fission systems, energy can be generated (reactors, sun, stars, radioactive atoms, … In particle accelerators, energy can be consumed, also everywhere in the universe cosmic rays became particles These are not common engineering systems For most applications: Accumulation = Net Input

14. Types of Energy Accumulation = Net Input State Energies Kinetic Potential Internal (Independent of Path) Path Energies Work Heat (Depend on Path)

15. Path Energies Work is an energy flow across a boundary from a driving force mechanical + shaft + hydraulic + electrical + chemical + laser Heat is an energy flow resulting from a temperature driving force. conduction + blackbody radiation

16. Mechanical Work Results from a force applied over a linear distance

17. Shaft Work Results from a twisting force (torque, T) applied over a circular distance θ

18. Pairs Exercise #1 A lawn mower engine is started by pulling a cord wrapped around a sheave. The radius of the sheave is 8.0 cm and the cord is wrapped around the sheave twice. If a constant force of 90 N is applied to the cord, what work is done?

19. Shaft Power Power = work/time Units are usually horsepower (hp)

20. Pairs Exercise #2 How much power (in hp) is produced if your automobile engine is producing 250 ft-lb of torque at 4000 rpm?

21. Hydraulic Work xx P1P1 P2P2 F Q = V/t (flow rate) W = F  x F = A(P 2 -P 1 ) W = A(P 2 -P 1 )  x Volume of fluid that flows: V=A  x W = V (P 2 -P 1 ) W = Qt (P 2 -P 1 ) A (area of piston face)

22. Pairs Exercise #3 Atmospheric-pressure water is pumped at rate of 15 gal/min into a 60-psig storage tank. A) How much work (in ft-lb) is done by the pump in one day assuming it pumps constantly for the 24-h period? B) What “size” pump (i.e., power requirements in hp) is required for this job?

23. Electrical Work In electricity, the driving force is a voltage potential difference. Electrons move from lower to higher potential; i.e., they flow uphill, just opposite to positive charges The force required to move a charge, q, a distance  x from voltage V 1 to V 2 is F = q(V 2 -V 1 )/  x

24. Electrical Work Current [Amperes] is charge/time, thus i = q/t, or q = it Therefore electrical work is:

25. Pairs Exercise #4 You buy a light bulb that uses 0.545 A (current) for your porch light (110 V). You leave your light on all weekend (48 hours). The electric company charges you 5.75 cents per kW-h (kilowatt-hour). How much does it cost to leave your light on all weekend?

26. Lasers and Photons LASER: Light Amplification by Stimulated Emission of Radiation The energy (E) of a photon (quantum of light) with frequency is E = h  Joules  = c/ E = hc  Joules h = Planck’s constant = 6.62 x 10 -34 J s c = speed of light = 3.0 x 10 8 m/s

27. Heat Heat is energy flow driven by temperature differences Two major types of heat flow: Conduction Blackbody radiation

28. Conduction Conduction equation A x Q/t k T2T2 T1T1 k = thermal conductivity Rate of heat conduction

29. Pairs Exercise #5 A 4-cm-thick insulator (k=2x10 -4 cal cm/(s cm 2 o C) has an area of 1000 cm 2. If the temperature on one side is 170 o C and the temperature on the other side is 50 o C, what is the heat transfer by conduction?

30. Black Body and Blackbody Radiation A black body adsorbs all incident electro- magnetic radiation, regardless of frequency or angle of incidence.electro- magnetic radiation A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation with a spectrum that is determined by the temperature alone, not by the body's shape or composition.thermal equilibriumblack-body radiation spectrum temperature Heat transfer between blackbodies: